The study of high frequency core loss measurement with large impedance angle

The measurement error of core loss by general AC meter method is very large, especially when the impedance angle of the core is closed to 90°. The DC meter method was adopted in this paper. The basic idea is to transform the input DC voltage into a PWM voltage exciting on the magnetic core by a DC/AC circuit, and the core loss is obtained by measuring the active power from input DC voltage. This DC meter method can avoid the influence of impedance angle of the DUT. However, with this DC method, any other losses excepting for core loss shall be excluded someway. Accepting for the solution to minimize the losses in DC/AC circuit itself, a calibration method with air-core inductor was proposed to effectively take off the losses in DC/AC circuit by mathematical formula of the curve fitting. The calibration method made the accuracy further improved. The verification test is build to validate that the DC meter method with the calibration mathematical formula of the losses except core loss is accurate enough for practical applications, even for the powder cores.